Transmitting apparatus and transmitting method

1. A transmitting apparatus, comprising: a first processor circuit; a second processor circuit; a modulation circuit; and a switch circuit, wherein the first processor circuit is configured to execute a generating process that includes mapping each of a plurality of bit strings to a symbol in predetermined order for each number of bits according to a multivalued degree of a multilevel modulation method, and generating a symbol information piece according to the symbol, wherein the modulation circuit is configured to modulate light in accordance with the symbol information piece based on the multilevel modulation method; wherein the second processor circuit is configured to execute a detecting process that includes detecting each of inputs of a plurality of data signals, wherein the switch circuit is configured to select the plurality of bit strings based on a detection result of inputs of the plurality of data signals, wherein the second processor circuit is further configured to execute a first selecting process when an input of each of the plurality of data signals is detected by the detecting process, the selecting process being configured to cause the switch circuit to select a bit string included in each of the plurality of data signals, and execute a second selecting process when an input of at least one of the plurality of data signals is not detected by the detecting process, the second selecting process being configured to cause the switch circuit to select a bit string included in the data signal the input of which is detected instead of the data signal the input of which is not detected such that the identical symbol information pieces are serially generated in the predetermined order, wherein the switch circuit is configured to output the plurality of bit strings from a plurality of output ports to the generating process in the first processor circuit, wherein the second selecting process is configured to cause the switch circuit to output a bit string included in the data signal the input of which is detected from at least two output ports among the plurality of output ports.

2. The transmitting apparatus according to claim 1 , wherein the second selecting process is configured to execute a third selecting process when the number of data signals the inputs of which are not detected and the number of data signals the inputs of which are detected are plural and equal among the plurality of data signals, the third selecting process being configured to individually select bit strings included in the data signals the inputs of which are detected instead of each of data signals the inputs of which are not detected.

3. The transmitting apparatus according to claim 1 , wherein the detecting process detects each of inputs of the plurality of data signals by determining whether an input source device of each of the plurality of data signals is implemented in the transmitting apparatus or not.

4. The transmitting apparatus according to claim 1 , wherein the detecting process is configured to detect each of inputs of the plurality of data signals by determining whether an input source device of each of the plurality of data signals has an operating state or not.

5. The transmitting apparatus according to claim 1 , wherein the first processor circuit is further configured to execute a giving process that includes giving a control bit relating to a control of the plurality of bit strings to each of the plurality of bit strings, wherein the giving process is configured to give the common control bit to the bit string included in the data signal selected instead of the other data signal the input of which is not detected among the plurality of bit strings based on a detection result of inputs of the plurality of data signals.

6. A transmitting method implemented by a transmitting apparatus, the transmitting method comprising: mapping each of a plurality of bit strings to a symbol in predetermined order for each number of bits according to a multivalued degree of a multilevel modulation method and generating a symbol information piece according to the symbol; modulating light in accordance with the symbol information piece based on the multilevel modulation method; detecting each of inputs of a plurality of data signals; and selecting the plurality of bit strings based on a detection result of inputs of the plurality of data signals, wherein a selector for the plurality of bit strings when an input of each of the plurality of data signals is detected, selects a bit string included in each of the plurality of data signals, and when an input of at least one of the plurality of data signals is not detected, selects a bit string included in the data signal the input of which is detected instead of the data signal the input of which is not detected such that the identical symbol information pieces are serially generated in the predetermined order, wherein the switch circuit is configured to output the plurality of bit strings from a plurality of output ports to the generating process in the first processor circuit, wherein the second selecting process is configured to cause the switch circuit to output a bit string included in the data signal the input of which is detected from at least two output ports among the plurality of output ports.